First to address the performance issue. Could you confirm that you have TubePress's API cache enabled from WP Admin > Settings > TubePress > Cache? Given your situation it's critical that this is turned on and working.

However, even with the API cache turned on we might still have a performance problem. Since you're asking TubePress to fetch 25 video sources (22 YouTube channels and 3 playlists), there's still a lot of server-side processing that needs to be done. I tested your shortcode on tubepress.com, a moderately high-performance VPS, and the page still took a few seconds to load.

I've tinkered with the idea of adding another cache tier to TubePress that would cache its raw HTML output, but there are a number of caching plugins for WordPress that do just that (e.g. WP Super Cache, WP Fastest Cache). Since you are running W3 Total Cache on your site, I think the best solution would be to simply ensure that your pages with TubePress are being served from W3 Total Cache's cache. Right now it doesn't seem that they are. Thoughts?

Finally, the pagination problem indeed seems to be a new bug. Thank you for reporting this. I'll be investigating tomorrow and will release a fix immediately. Please stand by for an update!

Eric, thanks, the new release seems to have fixed the pagination error.

Yes, I do have Tubepress cache enabled. I don't have any exlusion set up in W3TC for tubepress or the pages it's on, so I don't see why it wouldn't be caching them. There is an option "Cache SSL (https) requests" which I do NOT have checked - would that affect the tubepress pages, since the YouTube videos are coming from https servers?

As I said at the top of this thread, this was not an issue before 4.1.8, so it seems like it must be related to something you've changed in tubepress.

Eric, thanks, the new release seems to have fixed the pagination error.

Yes, I do have Tubepress cache enabled. I don't have any exlusion set up in W3TC for tubepress or the pages it's on, so I don't see why it wouldn't be caching them. There is an option "Cache SSL (https) requests" which I do NOT have checked - would that affect the tubepress pages, since the YouTube videos are coming from https servers?

As I said at the top of this thread, this was not an issue before 4.1.8, so it seems like it must be related to something you've changed in tubepress.

Glad to hear that we're making some progress! Strangely when I visited your site yesterday and today, the initial page load was very fast. Did you just recently switch to CloudFlare, too? CloudFlare usually strips out HTML comments so I can't really tell if W3TC is working, but regardless it certainly feels fast so I'd suspect that it's working normally.

However when clicking on page numbers in the TubePress gallery, we still see a very sluggish response. This is because W3TC doesn't cache Ajax requests, so TubePress does all that backend work for each page request. I think what I need to do is add the extra caching layer that I mentioned in my previous post. It shouldn't be that difficult and I should be able to knock it out quickly - hopefully over the next few days?

Nothing yet but another customer in a nearly identical situation just contacted us. I'm working on this feature and one other bug fix that I have planned. We're working as fast as possible - I'm sorry for the delay!